Alloy of tin, silver and nickel

ABSTRACT

An alloy of tin, silver, balance nickel and impurities is contemplated. The alloy in proportions is tin, 1 to 45 percent, preferably 20 to 45 percent, silver, 45 to 98 percent, balance, nickel and impurities.

United States Patent 1 [11] 3,778,259

Viglione Dec. 11, 1973 [54] ALLOY F TIN, SILVER AND NICKEL 1,896,410 2/1933 Leach 75/173 R 1 8 1934 L [76] Inventor: Gaetano Thomas Viglione, R.F.D. 811934 322 1, Amesbvfy, Mass- @1913 2,052,143 8/1936 Kern 75 173 R [22] Filed: June 21, 1972 [21] Appl. No.: 264,887 Primary ExaminerL. Dewayne Rutledge Assistant Examiner-E. L. Weise Related Apphcamm Data Attorney-Joseph Gray Jackson et al. [63] Continuation-impart of Ser. No. 145,514, May 20,

1971, Pat. No. 3,738,920.

[52] [1.5. CI. 75/134 B, 75/173 R, 75/175 R [57] ABSTRACT [51] Int. Cl. C226 /00 Field of Search 75/173 173 An alloy of tin, silver, balance nickel and impurities is 75/l75 134 134 F, 134 N contemplated. The alloy in proportions is tin, 1 to 45 percent, preferably to percent, silver, 45 to 98 Reielences Clted percent, balance, nickel and impurities.

UNITED STATES PATENTS 6/1870 Plumb /173 R 5 Claims, N0 Drawings ALLOY OF TIN, SILVER AND NICKEL The present application is a continuation-in-part of application Ser. No. 145,514, filed May 20, 1971 now U.S. Pat. No. 3,738,920, dated June 12, 1973 for PLATING TARNISI-l-lNl-IIBITED BRIGHT SILVER ALLOY.

A purpose of the invention is to deposit a tarnishinhibited bright silver alloy which resembles the noble metals especially platinum or white gold, but is much more economical.

A further purpose is to plate a tamish-inhibited bright silver alloy which is resistant to oxidation, from an alkaline cyanide water bath containing tin ion, silver ion and nickel ion.

A further purpose is to employ an alkaline cyanide water bath containing 3.0 to 30.0 grams per liter of tin ion, preferably 5.3 grams per liter of tin ion, 0.3 to 3.0 grams per liter of silver ion, preferably 0.65 grams per liter of silver ion, and 0.13 to 1.35 grams per liter of nickel ion, preferably 0.13 grams per liter of nickel ion.

A further purpose is to deposit an alloy of tin, silver and nickel in an attractive tarnish-inhibitive bright silver like deposit which is effective in coverage and continuity, firmly adherent and resistant to the forces of deterioration, commonly encountered by silverware such as flatware, tableware, for a reasonable time.

A further purpose is to produce an alloy having by weight to 45 percent of tin, preferably to 45 percent of tin and most desirably 25 to percent of tin by weight, 45 to 70 percent by weight of silver, preferably 50 to 70 percent by weight of silver, and most desirably 65 to 70 percent of silver, and the balance nickel and impurities.

A further purpose is to produce an alloy having by weight 29 percent of tin, 70 percent of silver and the balance nickel and impurities.

A further purpose is to produce an alloy having by weight 30 percent of tin, 69 percent of silver and the balance nickel and impurities.

A further purpose is to produce an alloy having by weight 20 percent of tin, 70 percent of silver and the balance nickel and impurities.

A further purpose is to produce an alloy having by weight 45 percent of tin, 45 percent of silver and the balance nickel and impurities.

A further purpose is to electroplate on a base of any of the common metals suitable for silverware (flatware and vessels), jewelry and the like, for example, steel, copper, brass, bronze and monel, applying the electroplating of the invention directly or if desired with intermediate layers, such as copper plating or nickel plating.

A further purpose is to use 20.5 grams per liter of tin ion, 2.5 grams per liter of silver ion and 0.1 grams per liter of nickel ion with varying current densities to produce an alloy having 1 to 19 percent of tin, 98 to 70 percent of silver and the balance nickel and impurities.

Further purposes appear in the specification and in the claims.

The present invention is believed to find its best application in the decorative arts such as the production of silverware (flatware and holloware), jewelry, decorative surfaces of appliances, instruments and machines, and for corrosion protection where appearance and physical properties are important, for example in instruments such as electrical instruments, mechanical instruments, hardware and components and the like.

In the prior art electrodeposited coatings including noble metals such as rhodium have been extensively developed as embodied in Keitel U.S. Pat. No. 1,779,436, granted Oct. 28, 1930 for Process of Electrodepositing Metals of the Platinum Group; Zschiegner U.S. Pat. No. 1,779,458, granted Oct. 28, 1930, for Electrodeposition of Platinum Metals; Bart U.S. Pat. No. 1,947,180, granted Feb. 13, 1934 for Tarnish-Resisting Silver; and Zimmerrnann U.S. Pat. No. 1,981,820, granted Nov. 30, 1934 for Process of Electrodepositing Rhodium, Bath and Method of Preparing the Same. In my U.S. Pat. No. 3,547,626, granted Dec. 15, 1970 for Plating Tarnish-Resistant Bright White Alloy I have described an alloy of cadmium, silver and nickel which is tarnish-resistant and resembles rhodium.

The present invention is concerned with the production of a bright silver alloy which resembles platinum or white gold, is much less expensive than a noble metal, and which has improved resistance against tarnishing in industrial atmospheres, provides corrosion resistance, firm adherence to the base metal and resists scuffing and abrasion encountered in silverware (flatware and holloware), jewelry, instrument parts and the like. As compared with the surface of silver, applied for example in flatware or holloware, the alloy of the invention is much more resistant from tarnishing, and requires treating or burnishing less often. In addition the alloy of the invention is produced in a single step from an electroplating bath of high speed, with a high rate of deposition if desired and of uniformly good appearance when the plating is controlled as explained in this application.

The electrodeposited layer can be applied with adequate appearance for many jewelry parts in a matter of a minute or less to obtain a plating layer having a thickness of 0.0001 inch, or it can be applied for the purpose of electroforming in order to make a thick deposit, even a deposit having a thickness for example as great as one-fourth inch or more.

The alloy of the invention lends itself to deposition on the common metals used in making inexpensive silverware, jewelry, appliances and instruments such as carbon and alloy steel, copper and copper base alloys such as brass and bronze, and the like. The coating of the invention can be applied over prior e1ectrodeposited layers which are employed for example for corrosion protection or to obtain a favorable color background as copper or nickel plate on steel.

One of the advantages of the alloy of the invention is that it has a whiteness and reflectance which resembles platinum or white gold and particularly resembles pure silver.

The alloy in the invention is tarnish-inhibitive. For example, it has been subjected to 10 percent solution of polysulfide at room temperature for 20 minutes without visible impairment in the brightness of the plated surface.

An unusual advantage which makes the alloy of the invention especially suited to silverware is that it resists attack of food acids such as acetic: acid, citric acid and other constituents of fruits and vegetables, making it peculiarly suited for exposure to such materials in the ordinary process of serving food and storing the food in a refrigerator.

The electroplating according to the invention is carried out in a cyanide water bath which of course is maintained alkaline, for example, in the presence of sodium or potassium hydroxide, that is in the concentration of 7 to 20 grams per liter. The pH of the plated bath is preferably maintained at about I 1.5 to 12.5.

The electrolyte has dissolved in it soluble salts providing tin ion, silver ion and nickel ion. In order to create such ions in the bath, the respective cyanides may be introduced or any well-known techniques may be used. For example, stannous chloride may be placed in the bath and dissolved by adding sodium cyanide. It will, of course, be evident that the conductivity of the bath can be increased if desired by adding sodium cyanide or other alkali conducting salts.

It is very desirable to maintain a proper balance of the concentration of tin ion, the concentration of silver ion and the concentration of nickel ion as suggested below.

The bath temperature can vary widely, but good results are obtained by plating in a temperature range between 125F. and 155F. The bath temperature may also be room temperature.

The voltage employed will suitably be in the range of 2 to 12 volts direct or unidirectional current. The current density will typically vary between and 60 amperes per square foot, and preferably between 25 and 60 amperes per square foot. For best results, a combination of insoluble and soluble anodes may be used, such as soluble anodes of silver and tin and an insoluble anode of stainless steel, platinum, titanium or carbon (graphite). The ratio of areas of anode to cathode should not exceed 1 to l.

The alloy obtained is an alloy of tin, silver and nickel, It may have the following weight proportions:

Component Broad Narrow Preferred Tin l-45 2545 25-30 Silver 45-98 5070 65-70 Nickel and a Balance Balance Balance Small Amount of Impurity The percentage of impurities in these alloys is not in excess of 0.50 percent (by weight).

EXAMPLE I The following electrolyte bath was made up in water:

tin ion 5.3 grams per liter silver ion 0.65 grams per liter nickel ion 0.13 grams per liter sodium hydroxide 15 grams per liter sodium cyanide 100 grams per liter Tin was added as tin hydroxide. The silver was added as silver cyanide. The nickel was added as nickel hydroxide.

Components suitable for jewelry and the like were made up consisting of low carbon steel, copper and brass. The components were cleaned of grease, foreign matter and oxide as well known in the procedure described in 2 Metals Handbook (8th Ed. 1964) 307 and following.

The bath was heated to 130F. plus or minus 5F., and maintained within that temperature range with constant stirring. An insoluble anode of stainless steel and a soluble anode of silver were used, with an anode to cathode ratio of l to l. The work was inserted as cathode and direct current was supplied between the anode and the cathode under a direct voltage of l to 1.5 volts at a current density of 15.0 amperes per square foot. The work was electroplated for 60 seconds in the above bath under the above conditions and a deposit was obtained which was silvery white and bright without burnishing. No porosity was visible, and the coating was tarnish-free after immersion in a 10 percent water solution of sodium sulfide for 5 minutes.

Spectrographic analysis showed that the electrodeposit had the following composition by weight:

Tin 26% Silver Nickel and Impurities Balance EXAMPLE 2 In order to make an alloy of higher tin content the preferred technique is to increase the bath temperature and plate at higher current density.

The procedure of Example 1 was followed except that the bath temperature was maintained at F. plus or minus 5, and the work was plated at a current density of 45 amperes per square foot. The alloy deposit in this case had the following composition by weight:

Tin 45% Silver 45% Nickel and Impurities Balance For a discussion of control of alloy content by temperature and current density see 1 Brenner Electrodeposition of Alloys (1963) p. 610, paragraph 19.2b.

EXAMPLE 3 By adjusting the temperature and current density I have obtained alloys having intermediate tin contents. Using a bath temperature of F. and a current density of 30 amperes per square foot I have obtained from this bath an alloy of the following composition by weight:

Tin 29% Silver 30% Nickel and Impurities Balance EXAMPLE 4 By plating at a bath temperature of 120F. and a current density of 20 amperes per square foot, I have obtained a coating having the following composition by weight:

Tin 30% Silver 69% Nickel and Impurities Balance EXAMPLE 5 An entirely different area of use is involved in the l to 19 percent tin alloys, silver 78 to 98 percent, nickel and some impurities balance. These alloys have particular interest in electrical goods such as power transmission fuses, where the composition of the alloys depends on the current density.

The electrolyte for production of such alloys is as follows:

Tin ion 20.5 grams per liter Silver ion 2.5 grams per liter Nickel ion 0.1 grams per liter Sodium hydroxide 15 grams per liter Sodium cyanide 100 grams per liter.

An insoluble anode was used with an anode to cathode ratio of 1:1.

With current density of 5 to 10 amperes per square foot an alloy composition will result as follows:

Tin l to 5% Silver 95 to 98% Nickel and impurities balance EXAMPLE 6 with the above eleclfolyte and the tfichnique f consisting of the following composition by weight:

ample 5, with slightly higher ampere density, the tendency is to increase the tin at the expense of the silver and nickel.

With a different density of 10 to amperes per square foot, the following alloy is obtained:

Tin 6 to 10% Silver 89 to 93% Nickel and impurities Balance EXAMPLE 7 Using the above technique with the above electrolyte, an ampere density of 16-25 amperes per square foot results in the following alloy:

Tin 11 to 19% Silver 78 to 88% Nickel and impurities Balance With higher concentrations in the electrolyte and higher ampere densities, higher compositions of tin in the alloys can be produced.

In view of my invention and disclosure, variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the composition shown, and I therefore claim all such insofar as they fall within the tin 25 to 30% silver 65 to nickel and impurities balance.

2. A tarnish-inhibited bright silver alloy essentialy consisting of the following composition by weight:

tin 29% silver 70% nickel and impurities balance.

3. A tarnish-inhibited bright silver alloy essentially consisting of the following composition by weight:

tin 30% silver 69% nickel and impurities balance.

4. A tarnish-inhibited bright silver alloy essentially consisting of the following composition by weight:

tin 45% silver 45% nickel and impurities balance.

5. An alloy essentially consisting of the following composition by weight:

tin l to 5% silver to 98% nickel and impurities balance. 

2. A tarnish-inhibited bright silver alloy essentialy consisting of the following composition by weight: tIn - 29% silver - 70% nickel and impurities - balance.
 3. A tarnish-inhibited bright silver alloy essentially consisting of the following composition by weight: tin - 30% silver - 69% nickel and impurities - balance.
 4. A tarnish-inhibited bright silver alloy essentially consisting of the following composition by weight: tin - 45% silver - 45% nickel and impurities - balance.
 5. An alloy essentially consisting of the following composition by weight: tin - 1 to 5% silver - 95 to 98% nickel and impurities - balance. 